Process of carburizing armor-plates.



Patented Oct. 3, |899.

.|. s. UNSER.

(Application @led June 9, 1898.)

PROGSS 0F GABBURIZING ARMOR PLATES.

um Modal.)

INVENTOR WITNESSES HWI/W N6. 634,25l. Patented' out. 3, 1899.

\ ,1. s. utmsi.A PRUCESS -UF GARBURIZING FHUDB PLATES.

(Application Bled June 9, 1898.) (No Model.) 2 Sheets-Sheet 2,

WITNESSES INVENTOR QQ/m7@ m: cams PErERs oo., moito-umm WASHINGTON, uA c.

.IOHN S. UNGER, OF HOMESTEAD, PENNSYLVANIA, ASSIGNOR TO THE OAR- NEGIE STEEL COMPANY, LIMITED, OF PITTSBURG, PENNSYLVANIA.

PROCESS OF CARBURIZING ARMOR-PLATES.

SPECIFICATION forming part of Letters Patent No. 634,251, dated October 3, 1899. A Applioationled June 9, 18.98- Serial No. 682,985. (No model.)

To @ZZ whont it 11m/y concern:

Be it known that I, JOHN S. UNGER, of Homestead, in the county of Allegheny and State of Pennsylvania, have invented a new and useful Improvement in Carburizing Armor-Plates, of which the following is a full, clear, and exact description, reference being had to the accompanying drawings, forming part of this specification, in which- Figure l is a longitudinal sectional elevation of the gas-furnace or heating-chamber, showing the movable hearth in place. Fig. 2 is a horizontal section ou the line II II of Fig. l.

My invention relates to the supercarburization of plates or pieces of steel and is especially designed to be applied in the manufacture of armor-plate or of masses of steel to be shaped into armor-plate.

My invention is based on the discovery7 that carburization can bev conducted most rapidly and most efficiently by using as the carburizing agent soot, the-amorphous form in which carbon is deposited as the result of the decomposition of hydrocarbon gases.

I shall now describe the preferable mode of lpracticing my invention, referring to Fig. l,

in which 2 represents a heating-furnace having at the opposite sides gas-ports 3, through which the heating-gas is introduced at one side of the furnace and discharged after combustion at the other side. t is a movable hearth common in furnaces of this type, carried on a truck 5, mounted on-wheels 6 and adapted to be moved into and out of the heating-chamber by a suitable motor 7. The plates of armor-steel are placed on the hearth with the faces to be carburized toward each` other and separated by interposed billets or supports 9. A gas-pipe l0, adapted to deliver hydrocarbon gas, is inserted into the space 11 between the armor-plates. An outlet for the gas is also provided at l2 by drilling at any convenient spot a hole, and said space is sealed through one of its billets, and said space is otherwise sealed to exclude the air by lutin g with clay the joints between the billets. Intermediate sagblocks, like the blocks 16, (shown in Fig. 2,) may also be employed where the plates are of large area. rI his is the arrangement which has commonly been adopted for supercarburizing armorplate by the gas-treatment process. In such process it has been the practice first to heat the plates by the passage of Iiame through the heating-chamber 2 until they are brought to a high temperature of about from 875D to 1,000O centigrade, and after the plates have been thus heated to` introduce through the pipe 10 into the space between the plates a 6o current of hydrocarbon gas, which is caused to flow through the space and out of the outlet l2 fora period of six days or more, thus gradually carburizing the inner faces of the plates. When the gas thus introduced comes into the highly heated space between the plates, it is decomposed and deposits solid carbon upon the surfaces, and it is this deposited carbon which is absorbed by the metal and performs the work of carburization; but 7o the carbon thus deposite-d at the high temperature'of the furnace is graphitic, and I, have discovered that by modifying the conditions so that an initial layer of amorphous carbon or soot is deposited upon the faces of the steel plates the carburizing operation can be conducted more rapidly and with better results than is otherwise possible. This I effect by introducing the hydrocarbon gas at an earlier stage than heretofore,whi1e the armor-plate is 8o at a lower heat, such that the carbon will be deposited from the gas as amorphous carbon and not as graphite. Thus when the plate has been heated sutliciently to show a faint color, say a temperature of about 550o centigrade, I introduce the hydrocarbon gas from the pipe 10. The consequence is that the faces of the plates will be covered with a layer of amorphous carbon or soot deposited from the gas, and when the plates afterward become more 9o highly heated and the carbon deposit becomes graphitic in its nature the graphitic carbon is deposited upon and as a covering for the inner layer of amorphous carbon. The layer of carbon next to the steel surface being amorphous is in the most active and efficient condition in which it can be presented. The heating is continued and the temperature maintained at about 875o to 1,000o centigrade for six days or more, according to the thickroo ness of the plates, until the desired degree of carburization has been effected. Specifically I would state for the information of those practicing inyinvention that a plate six inches thick in a furnace constructed as shown in the drawings should be maintained at a teinperature of 9000 eentigrade for about nine days or at 1,0000 centigrade for about seven days in order to produce with my invention the degree of carbu rization ordinarilydesired in armor-plate, the length of the operation necessary for different degrees of carburization being varied, as will be understood by those skilled in the art, accordingly as the tempera-ture is kept at a higher or lower degree and as the plate treated is thicker or thinner. By my invention applied in this way the steel absorbs the carbon readily and quickly, enabling me to perform the work at lower temperature (say 0000 centigrade) than has been common heretofore without unduly prolonging the operation and by using` such lower temperature to avoid the danger of semifusing the surface of the plate, or when I use higher temperatures, say 0000 to 1,0000 centigrade, my invention enables nie to perform lthe work in much less time than heretofore. V

I believe I am the iirst to bring the gas into Contact with the armor-plate to be earburized before the plates are brought to full working temperature of 8750 to 1,0000 centigrade.

I claim- 1. The process herein described for supcr carburizing steel for armor-plates and other purposes, which consists in heating the steel to a relatively low temperature, sufficient to cause the decomposition of hydrocarbon gas and the deposit therefrom of amorphous carbon or soot, bringing such gas into contact with the steel so heated, and excluding air, thereby depositing a layer ef amorphous carbon upon the steel, then continuing at a higher temperature and for a period of days the heating of the plate and the admission of gas thereto, and depositing graphitic carbon upon the plate at such higher temperature; substantially as described.

' 2. The process herein described for supercarburizing steel-for arxnor-plates and other purposes, which consists in introducing into contact with the steel hydrocarbon gas while the steel is at a temperature less than the working temperature of 8750 to 1,0000 centigrade, thereby causing a deposit of carbon at a relatively low heat, and then raising the temperature to the working point, continuing.

the heating and admission of gas for a period of days, and depositing graphitic carbon upon the plate at such higher temperature; substantially as described.

In testimony whereof I have hereunto set my hand.

JOHN S. UNGER.

Witnesses Tnonms W. BAKEWELL, ll. M. ConwIN. 

